A known thermoelectric module, which uses Peltier effect, includes plural peltier elements and receives supplies of electric power to cool and/or heat various devices (e.g., disclosed in JPH09-55541, i.e., hereinafter referred to as Patent reference 1). The thermoelectric module of this kind is applied for regulating the temperature of an optical communication device, for example, more particularly, a laser diode for optical fiber. In response to an increase of data communication quantity in accordance with changes in communication environment, greater number of thermoelectric modules is requested to be provided. Further, in order to provide greater number of the thermoelectric modules while avoiding an increase of the optical communication device in size, downsizing of components of the thermoelectric module is requested.
The thermoelectric module includes insulating substrates and plural thermoelectric conversion elements (peltier element) mounted onto the insulating substrates. Thus, when manufacturing the thermoelectric module, processes for forming plural electrodes on the insulating substrates and for mounting the peltier elements on the electrodes are required. In view of enhancing manufacturing efficiency, or productivity for manufacturing the thermoelectric modules, it is favorable that the process for mounting the peltier elements on the electrodes is automatically conducted by a mounter, a mounting device. In order to automatically mount the peltier elements on the electrodes, positions of the electrodes on the insulating substrates need to be accurately recognized.
In order to accurately recognize the position of the electrodes on the insulating substrates, for example, the insulating substrate on which the electrodes are formed may be recognized as images, the positional relationship of the plural electrodes, or the positional relationship of the plural electrodes relative to the entire insulating substrate may be obtained, and further, the positions of the electrodes may be obtained.
It is considered to provide a difference in lightness (brightness, value) or saturation (chrome) of plural objects to be recognized in order to perform the image recognition of the insulating substrate on which the electrodes are formed with high precision. However, because the difference in the lightness or the saturation of the insulating substrate and the electrodes is relatively small, it is difficult to recognize the position of the electrodes on the insulating substrate with high precision while recognizing the electrodes which are on the insulating substrate as images, that is, it is difficult to recognize the position of the electrodes on the insulating substrate with high precision while recognizing the electrodes with a background of the insulating substrate as images. It is considered that the position of the electrodes on the insulating substrate can be accurately, or substantially accurately recognized by performing the image recognition with a construction that a mark (mark for image recognition) whose lightness (brightness, value) and/or saturation (chroma) for image recognition differ from those of the insulating substrate.
In those circumstances, as described above, because there is needs for the downsizing of the components of the thermoelectric module, there is no room for arranging a mark for image recognition on the insulating substrate between adjacent electrodes. Thus, the mark for image recognition needs to be formed at the electrode. Patent reference 1 discloses a technology in which a slit is provided at a center portion of the electrode and at a peripheral portion of the electrode. In Patent reference 1, the slit is provided to eliminate the air forming the void at a solder joint portion between the electrode and the thermoelectric conversion element. However, according to the electrode disclosed in Patent reference 1, it is considered that the slit per se functions as a mark for image recognition because of the shade projected in the slit, which enhances the precision for the image recognition explained above.
On the other hand, according to the electrode disclosed in Patent reference 1, because the slit is provided, it is impossible to use the entire electrode as a conduction path. For example, considering the precision, or accuracy of the image recognition, it is favorable that the dimension of the mark for the image recognition is equal to or longer than 0.2 millimeters, whereas a width of an electrode, generally, is equal to or shorter than 0.4 millimeters at the thermoelectric module for an optical communication device. Thus, in case of providing a mark for image recognition on the electrode, the width of the electrode available for the electric conduction is possibly assumed to be equal to or less than a half of the entire width of the electrode. The electrode with the foregoing construction is inferior in conductivity and may hinder the performance of the thermoelectric module from enhancing. Further, according to the electrode with the foregoing construction, electrical resistance is increased at an upstream portion of the conduction path of the slit. Accordingly, the enhancement of the performance of the thermoelectric module may be hindered due to the heat loss at the electrode.
A need thus exists for a thermoelectric module which is not susceptible to the drawback mentioned above.